1. Field of the Invention
The present invention relates to lawnmower blades, and more specifically, a replaceable insert for a rotary lawnmower blade.
2. Description of the Related Art
In the past, the sharpening of a mower blade required the removal of the entire blade. Once the blade was removed, a new edge could be ground or filed onto the blade. The blade would then have to be remounted onto the shaft. This procedure is difficult and time consuming. Various types of replaceable cutters have been proposed to avoid the resharpening and eventual loss of the rotary blade. Such replaceable blades have presented problems of one type or another with regard to the requirement of complex fabrications, strength of the replaceable cutter, weakened resistance to damage by foreign objects, and costs. In addition, there is the difficulty associated with stabilizing the blade in light of significant centrifugal forces, which fatigue the fasteners, bolts, rivets, etc. between the separable cutting edge and the main blade assembly.
Another problem with the blade assemblies of the prior art having separable cutting edges, is that the force of impact with an obstruction such as a rock or a root causes undue strain on the fasteners connecting the separable edge to the main blade assembly.
Related art blades having separable cutting edges sometimes require 5 horse power or more simply to rotate the blade due to the weight of the cutting edge attachments. Similarly, the separable cutting edge of the prior art is typically thicker and the blade assembly, to which the cutting edge is attached, requires larger bolts due to the lack of a stabilizing recess, which further increases the weight and thus the required horsepower. Finally, the problem with having a separable cutting edge retained by fasteners alone, as opposed to by a recessed shoulder, is the additional trouble involved with changing the blades, and the tools required to do so properly.
The present invention addresses the above problems that are evident in the following patents:
U.S. Pat. No. 4,229,933 issued October 1980 to Bernard discloses a separable mower blade having a slotted hole on the mower blade for reception of a bolt. The blade and stem are constructed so as to allow easy removal of the blade. However, Bernard does not disclose a recess and shoulder on the main blade assembly for reception of the cutting blade, and therefore, the bolt carries the load created by the spinning of the assembly, rather than the walls of the recess carrying the load.
U.S. Pat. No. 3,327,460 issued September 1964 to Blackstone teaches a blade assembly for a rotary mower that includes separable cutting blades but not inserts per se.
U.S. Pat. No. 5,303,535 issued April 1994 to Smith shows a mower blade with a separable cutting surface but no outside shoulder to counteract centrifugal force as in the present invention, and it requires large bolts requiring tools, to hold the cutting surface in place.
U.S. Pat. No. 5,467,586 issued November 1995 to Lin et al. teaches a replaceable cutting blade having multiple parts including a cover plate, multiple fasteners, but no outside shoulder.
U.S. Pat. No. 4,712,364 issued December 1987 to Oxley discloses a quick attachable and detachable mower blade assembly. U.S. Pat. No. 2,932,147 issued June 1957 to J. T. Beeston, Jr. shows an expendable cutting blade for a rotary mower. U.S. Pat. No. 2,898,725 issued August 1959 to J. F. Roesel discloses a rotary mower blade assembly having retractable blades. U.S. Pat. No. Re. 31,542 issued March 1980 to Hetrick shows a safety attachment for lawn mowers. British Pat. No. GB 2 036 524 to Houle, published July 1980 to Houle teaches a safety blade made from comminuted waste rubber.
U.S. Pat. No. Des. 357,691 issued April 1995 to Bryant illustrates a design patent for a one-piece lawn mower blade.
U.S. Pat. No. Des. 289,524 issued April 1987 to Andersson et. al. shows another design not suggestive of the present invention.
None of the above inventions and patents, taken either singularly or in combination, is seen to describe the instant invention as claimed. Thus a lawnmower blade solving the aforementioned problems is desired.